Hydroxyphenyl-piperidin-4-ylidene-methyl-benzamide derivatives for the treatment of pain

ABSTRACT

Compounds of general formula I  
                 
 
     R 1  is selected from any one of phenyl, pyridinyl, thienyl, furanyl, imidazolyl, triazolyl and thiazolyl;  
     where each R 1  phenyl ring and R 1  heteroaromatic ring may optionally and independently be further substituted by 1, 2 or 3 substituents selected from straight and branched C 1 -C 6  alkyl, NO 2 , CF 3 , C 1 -C 6  alkoxy, chloro, fluoro, bromo, and iodo. The substitutions on the phenyl ring and on the heteroaromatic ring may take place in any position on said ring systems;  
     are disclosed and claimed in the present application, as well as salts and pharmaceutical compositions comprising the novel compounds and their use in therapy, in particular in the management of pain.

FIELD OF THE INVENTION

[0001] The present invention is directed to novel compounds, to aprocess for their preparation, their use and pharmaceutical compositionscomprising the novel compounds. The novel compounds are useful intherapy, and in particular for the treatment of pain.

BACKGROUND AND PRIOR ART

[0002] The δ receptor has been identified as having a role in manybodily functions such as circulatory and pain systems. Ligands for the δreceptor may therefore find potential use as analgesics, and/or asantihypertensive agents. Ligands for the δ receptor have also been shownto possess immunomodulatory activities.

[0003] The identification of at least three different populations ofopioid receptors (μ, δ and κ) is now well established and all three areapparent in both central and peripheral nervous systems of many speciesincluding man. Analgesia has been observed in various animal models whenone or more of these receptors has been activated.

[0004] With few exceptions, currently available selective opioid δligands are peptidic in nature and are unsuitable for administration bysystemic routes. One example of a non-peptidic δ-agonist is SNC80(Bilsky E. J. et al., Journal of Pharmacology and ExperimentalTherapeutics, 273(1), pp. 359-366 (1995)). There is however still a needfor selective δ-agonists having not only improved selectivity, but alsoan improved side-effect profile.

[0005] Thus, the problem underlying the present invention was to findnew analgesics having improved analgesic effects, but also with animproved side-effect profile over current μ agonists, as well as havingimproved systemic efficacy.

[0006] Analgesics that have been identified and are existing in theprior art have many disadvantages in that they suffer from poorpharmacokinetics and are not analgesic when administered by systemicroutes. Also, it has been documented that preferred δ agonist compounds,described within the prior art, show significant convulsive effects whenadministered systemically.

[0007] We have now found that certain compounds not specificallydisclosed by, but included within the scope of WO 98/28275, exhibitsurprisingly improved δ-agonist properties and in vivo potency.

OUTLINE OF THE INVENTION

[0008] The novel compounds according to the present invention aredefined by the formula I

[0009] wherein

[0010] R¹ is selected from any one of

[0011] where each R¹ phenyl ring and R¹ heteroaromatic ring mayoptionally and independently be further substituted by 1, 2 or 3substituents selected from straight and branched C₁-C₆ alkyl, NO₂, CF₃,C₁-C₆ alkoxy, chloro, fluoro, bromo, and iodo. The substitutions on thephenyl ring and on the heteroaromatic ring may take place in anyposition on said ring systems.

[0012] A preferred embodiment of the present invention is a compoundaccording to FIG. I wherein R¹ is as defined above and each R¹ phenylring and R¹ heteroaromatic ring may independently be further substitutedby a methyl group.

[0013] A more preferred embodiment of the present invention is acompound according to FIG. I wherein R¹ is pyridinyl, thienyl orfuranyl.

[0014] Within the scope of the invention are also salts and enantiomersof the compounds of the formula I, including salts of enantiomers.

[0015] When the phenyl ring and the heteroaromatic ring(s) aresubstituted, the preferred substituents are selected from anyone of CF₃,methyl, iodo, bromo, fluoro and chloro.

[0016] Reaction step g in Scheme 1, vide infra, is performed by reactingan intermediate compound of the general formula II

[0017] wherein PG is a urethane or benzyl-like protecting group, such asBoc, with 3-hydroxyphenyl boronic acid, using a palladium catalyst, e.g.Pd(PPh₃)₄, in the presence of a base, e.g. Na₂CO₃, to give the compoundsof general formula III,

[0018] which is thereafter deprotected, under standard conditions andalkylated under reductive conditions with a compound of the generalformula R¹—CHO to give compounds of the general formula I.

[0019] Suitable palladium catalysts include, but is not limited to,PdCl₂ (with a phosphine), Pd(OAc)₂ (with a phosphine), Pd(dba)₂,PdCl₂(dppf) CH₂Cl₂, Pd(PPh₃)₄, Pd/C.

[0020] Suitable bases include, but is not limited to, triethylamine,sodium and potassium carbonate.

[0021] Suitable reducing agents to be used includes, but is not limitedto, sodium cyanoborohydride and sodium triacetoxyborohydride.

[0022] The novel compounds of the present invention are useful intherapy, especially for the treatment of various pain conditions such aschronic pain, neuropathic pain, acute pain, cancer pain, pain caused byrheumatoid arthritis, migraine, visceral pain etc. This list shouldhowever not be interpreted as exhaustive.

[0023] Compounds of the invention are useful as immunomodulators,especially for autoimmune diseases, such as arthritis, for skin grafts,organ transplants and similar surgical needs, for collagen diseases,various allergies, for use as anti-tumour agents and anti viral agents.

[0024] Compounds of the invention are useful in disease states wheredegeneration or dysfunction of opioid receptors is present or implicatedin that paradigm. This may involve the use of isotopically labelledversions of the compounds of the invention in diagnostic techniques andimaging applications such as positron emission tomography (PET).

[0025] Compounds of the invention are useful for the treatment ofdiarrhoea, depression, anxiety, urinary incontinence, various mentalillnesses, cough, lung oedema, various gastrointestinal disorders,spinal injury and drug addiction, including the treatment of alcohol,nicotine, opioid and other drug abuse and for disorders of thesympathetic nervous system for example hypertension.

[0026] Compounds of the invention are useful as an analgesic agent foruse during general anaesthesia and monitored anaesthesia care.Combinations of agents with different properties are often used toachieve a balance of effects needed to maintain the anaesthetic state(eg. amnesia, analgesia, muscle relaxation and sedation). Included inthis combination are inhaled anaesthetics, hypnotics, anxiolytics,neuromuscular blockers and opioids.

[0027] Also within the scope of the invention is the use of any of thecompounds according to the formula I above, for the manufacture of amedicament for the treatment of any of the conditions discussed above.

[0028] A further aspect of the invention is a method for the treatmentof a subject suffering from any of the conditions discussed above,whereby an effective amount of a compound according to the formula Iabove, is administered to a patient in need of such treatment.

[0029] A further aspect of the present invention is intermediates of thegeneral formula II,

[0030] wherein PG is a urethane or benzyl-like protecting group, such asBoc,

METHODS OF PREPARATION

[0031] The compounds according to the present invention may be preparedby following the known procedures described in e.g. “Advanced OrganicChemistry” third edition. by Jerry March, John Wiley and Sons Inc.; NewYork (1985): Step (a): p848; Step (b): p848; Step (c): p657; Step (d):p875; Step (e): p371-373; Step (f):p364-366; Step (g): N. Miyaura and A.Suzuki, Chem. Rev., 95, 2457-2483(1995); Step (h): “Protective Groups inOrganic synthesis” p 327-329, by Theodora W. Greene and Peter G. M.Wuts, Second Edition, John Wiley and Sons Inc.; New York (1991). Thesereferences are hereby incorporated in full.

EXAMPLES

[0032] The invention will now be described in more detail by thefollowing Examples, which are not to be construed as limiting theinvention.

Example 1 Preparation ofN,N-diethyl-4-(3-hydroxylphenyl-piperidin-4-ylidene-methyl)-benzamide(Compound 7)

[0033] (i) Preparation of4-(4-methoxycarbonyl-benzylidene)-piperidine-1-carboxylic acidtert-butyl ester (compound 3)

[0034] A mixture of compound 1 (11.2 g, 49 mmol) and trimethyl phosphite(25 mL) was refluxed under N₂ for 5 hrs. Excess trimethyl phosphite wasremoved by co-distillation with toluene to give compound 2 inquantitative yield: ¹H NMR (CDCl₃) δ3.20 (d, 2H, J=22 Hz), 3.68 (d, 3H10.8 Hz), 3.78 (d, 3H, 11.2 Hz), 3.91 (s, 3H), 7.38 (m, 2H), 8.00 (d,2H, J=8 Hz).

[0035] (ii) To a solution of the above product (compound 2) in dry THF(200 mL) was added dropwise lithium diisopropylamide (32.7 mL 1.5 M inhexanes, 49 mmol) at −78° C. The is reaction mixture was then allowed towarm to room temperature prior to addition ofN-tert-butoxycarbonyl-4-piperidone (9.76 g, 49 mmol in 100 mL dry THF).After 12 hrs, the reaction mixture was quenched with water (300 mL) andextracted with ethyl acetate (3×300 mL). The combined organic phaseswere dried over MgSO₄ and evaporated to give a crude product, which waspurified by flash to provide compound 3 as a white solid (5.64 g, 35%):

[0036] IR (NaCl) 3424, 2974, 2855, 1718, 1688, 1606, 1427, 1362, 1276cm⁻1;

[0037]¹H NMR (CDCl₃) δ1.44 (s, 1H), 2.31 (t, J=5.5 Hz, 2H), 2.42 (t,J=5.5 Hz, 2H), 3.37 (t, J=5.5 Hz, 2H), 3.48 (t, J=5.5 Hz, 2H), 3.87(s,3H), 6.33 (s, 1H), 7.20 (d J=6.7 Hz, 2H), 7.94 (d, J,=6.7 Hz, 2H); ¹³CNMR (CDCl₃) δ28.3, 29.2, 36.19, 51.9, 123.7, 127.8, 128.7, 129.4, 140.5,142.1, 154.6, 166.8.

[0038] (iii) Preparation of4-bromo-4-[bromo-(4-methoxycarbonyl-phenyl)-methyl]-piperidine-1-carboxylicacid tert-butyl ester (compound 4)

[0039] To a mixture of compound 3 (5.2 g, 16 mmol) and K₂CO₃ (1.0 g) indry dichloromethane (200 mL) was added a solution of bromine (2.9 g, 18mmol) in 30 mL CH₂Cl₂ at 0° C. after 1.5 hrs at room temperature, thesolution after filtration of K₂CO₃ was condensed. The residue was thendissolved in ethyl acetate (200 mL), washed with water (200 mL), 0.5 MHCl (200 mL) and brine (200 mL), and dried over MgSO₄. Removal ofsolvents provided a crude product, which was recrystallized frommethanol to give compound 4 as a white solid (6.07 g, 78%): IR (NaCl)3425, 2969, 1725, 1669, 1426, 1365, 1279, 1243cm⁻¹;

[0040]¹H NMR (CDC1₃) δ1.28 (s, 9H), 1.75 (m, 2H), 1.90 (m, 2H), 2.1 (m,4H), 3.08 (br, 4H), 3.90 (s, 3H), 4.08 (br, 4H), 5.14 (s, 1H), 7.57 (d,J=8.4 Hz, 2H) 7.98 (d, J=8.4 Hz, 2H);

[0041]¹³C NMR (CDCl₃) δ28.3, 36.6, 38.3, 40.3, 52.1, 63.2, 72.9, 129.0,130.3, 130.4, 141.9, 154.4, 166.3.

[0042] (iv) Preparation of4-[bromo-(4-caboxy-phenyl)-methylene]-piperidine-1-carboxylic acidtert-butyl ester (compound 5)

[0043] A solution of compound 4 (5.4 g 11 mmol) in methanol (300 mL) and2.0 M NaOH (100 mL) was heated at 40° C. for 3 hrs. The solid wascollected by filtration, and dried overnight under vacuum. The dry saltwas dissolved in 40% acetonitrile/water, and was adjusted to pH 2 usingconcentrated HC1. The desired product compound 5 (3.8 g, 87%) wasisolated as a white powder by filtration: ¹H NMR (CDCl₃) δ1.45 (s, 9H),2.22 (dd, J=5.5 Hz, 6.1 Hz, 2H), 2.64 (dd, J=5.5 Hz, 6.1 Hz, 2H), 3.34(dd, J=5.5 Hz, 6.1 Hz, 2H), 3.54 (dd, J=5.5 Hz, 6.1 Hz, 2H), 7.35 (d,J=6.7 Hz, 2H), 8.08 (d, J=6.7 Hz, 2H); ¹³C NMR (CDCl₃) δ28.3, 31.5,34.2, 44.0, 115.3, 128.7, 129.4, 130.2, 137.7, 145.2, 154.6, 170.3;.

[0044] (v) Preparation of4-[bromo-(4-diethylcarbamoyl-phenyl)-methylene]-piperidine-1-carboxylicacid tert-butyl ester (compound 6)

[0045] To a solution of compound 5 (1.0 g, 2.5 mmol) in drydichloromethane (10 mL) at −20° C. was added isobutylchloroformate (450mg, 3.3 mmol). After 20 min at −20° C. diethylamine (4 mL) was added andthe reaction was allowed to warm to room temperature. After 1.5 hrs thesolvents were evaporated and the residue was partitioned between ethylacetate and water. The organic phase was washed with brine and driedover MgSO₄. Removal of solvents provided a crude product, which waspurified by flash chromatography to give compound 6 as white needles(800 mg, 73%): IR (NaCl) 3051, 2975, 1694, 1633, 1416, 1281, 1168, 1115cm⁻¹; ¹H NMR (CDCl₃) δ1.13 (br, 3H), 1.22 (br, 3H), 1.44 (s, 9H), 2.22(t, J=5.5 Hz, 2H), 2.62 (t, J=5.5 Hz, 2H), 3.33 (m, 4H), 3.55 (m, 2H),7.31 (d, J=8.0 Hz, 2H), 7.36 (d, J=8.0 Hz, 2H); ¹³C NMR (CDCl₃) δ12.71,14.13, 28.3, 31.5, 34.2, 39.1, 43.2, 79.7, 115.9, 126.3, 129.3, 136.8,137.1, 140.6, 154.6, 170.5.

[0046] (vi) Preparation of 3-hydroxylphenyl boronic acid

[0047] 3-Bromophenol (8.65 g, 50 mmol) in dry THF (150 mL) was treatedwith sodium hydride (60%, 2.4 g, 60 mmol) at r.t. After 1 h,sec-butyllithium (1.3 M, 50 mL, 65 mmoL) was added dropwise to thereaction solution at −78° C. The reaction mixture was then allowed tostir at the same temperature for 30 min prior to addition of trimethylborate (15 mL). After warming up to r.t. for 2 hrs, the reaction mixturewas quenched with water (50 mL), and extracted with dichloromethane(2×100 mL). The combined organic phases were dried over MgSO₄ andevaporated to give the title compound as a white solid (4.0 g, 58 %),which was used in the Suzuki coupling reactions without furtherpurification.

[0048] (vii) Preparation ofN,N-diethyl-4-(3-hydroxylphenyl-piperidin-4-ylidene-methyl)-benzamide(compound 7)

[0049] A mixture of compound 6 (451 mg, 1.0 mmol), 3-hydroxylphenylboronic acid (230 mg, 1.7 mmol), 2M Na₂CO₃ (2.5 mL), andtetrakis(triphenyl phosphine) palladium(0) (20 mg) in toluene (degassed,5 mL) and ethanol (degassed, 5 mL) was refluxed at 90° C. for 4 hrsunder N₂. The reaction mixture was then cooled down to r.t., andextracted with ethyl acetate (2×100 mL). The combined organic phaseswere dried over MgSO₄ and evaporated to give a crude product.

[0050] The above product was treated with 4.0 M HC1 in dioxane at 50° C.for 2 h. After evaporation, the residue was dissolved in 1 M HCl (100mL) and impurities were extracted with diethyl ether (3×100 mL). Theaqueous phase was basified with NH₄OH and extracted with dichloromethane(3×100 mL). The combined organic phases were washed with brine, driedover MgSO₄ and evaporated to give the title compound 7 (305 mg, 88%):¹H-NMR (400 MHz, CDCl₃) δ1.12 (3 H, br m, CH₃CH₂—), 1.23 (3 H, br m,CH₃CH₂—), 2.33 (4 H, m, piperidine CH—), 2.89 (4 H, m, piperidine CH—),3.29 (3 H, br m, NH & CH₃CH₂N—), 3.53 (2 H, br m, CH₃CH₂N—), 4.71 (1H,s, OH), 6.57 (2 H, m, ArH), 6.65 (1 H, m, ArH), 7.09 (1 H, m, ArH), 7.12(2 H, d, J=8.0 Hz, ArH), 7.28 (2 H, d, J=8.0 Hz, ArH); Its HCl salt:m.p.>130° C. (December); IR (NaCl) 2975, 1598, 1442, 1293 cm⁻¹.

Example 2 Preparation ofN,N-diethyl-4-(3-hydroxylphenyl-N-benzyl-piperidin-4-ylidene-methyl)-benzamide(Compound 9)

[0051] (i) Preparation ofN,N-diethyl-4-(bromo-N-benzyl-piperidin-4-ylidene-methyl)-benzamide(compound 8)

[0052] Compound 6 prepared in Example 1(v) above (2.26 g, 5.0 mmoL), wastreated with TFA (25 mL) in dichloromethane (25 mL) at room temperature.After 2 h, the reaction mixture was condensed to give a residue, whichwas dissolved in acetonitrile (20 mL), and was reacted with benzylbromide ( 5.0 mmol) at r.t. for 2 h. The reaction mixture was condensed,and then dissolved in ethyl acetate (100 mL). The organic solution werewashed with 1N NH₄OH and brine, dried over MgSO₄. Removal of solventsprovided a crude product, which was purified by flash chromatography togive compound 8 as an oil (1.0 g, 45%): IR (NaCl) 2971, 1630, 1427,1287, 1094 cm ⁻¹; ¹HNMR (CDCl₃) δ1.13 (br, 3H), 1.23 (br, 3H), 2.28 (m,2H), 2.37 (m, 2H), 2.55 (m, 2H), 2.69 (m, 2H), 3.27 (m, 2H), 3.53 (br,4H), 7.31 (m, 4H).

[0053] (ii) Preparation ofN,N-diethyl-4-(3-hydroxylphenyl-N-benzyl-piperidin-4-ylidene-methyl)-benzamide(compound 9)

[0054] A mixture of compound 8 prepared in step (i) above (600 mg, 1.36mmol), 3-hydroxylphenyl boronic acid (414 mg, 3.0 mmol), 2M Na₂CO₃ (3.0mL), and tetrakis(triphenyl phosphine) palladium(0) (20 mg) in toluene(degassed, 5 mL) and ethanol (degassed, 5 mL) was refluxed at 90° C. for2 hrs under N₂. The reaction mixture was then cooled down to r.t. andextracted with ethyl acetate (2×100 mL). The combined organic phaseswere washed with brine, dried over MgSO₄. Removal of solvents provided acrude product, which was purified by flash chromatography to give thedesired title compound 9 (482 mg, 78%): IR (NaCl) 3350, 2974, 1606,1442, 1291 cm⁻¹; ¹H-NMR (400 MHz, CDCl3) δ1.11 (3 H, br m, CH3CH₂—),1.24 (3 H, br m, CH₃CH₂—), 2.36 (4 H, m, piperidine CH—), 2.46 (4 H, m,piperidine CH—), 3.26 (2 H, br m, CH₃CH₂N—), 3.53 (4 H, br m, PhCH₂N &CH₃CH₂N—), 6.53 (1 H, m, ArH), 6.57 (1 H, m, ArH), 6.63 (1 H, m, ArH),7.07 (3 H, m, ArH), 7.25 (7 H, m, ArH).

Examples 3-11

[0055] Compounds 10-18 of Examples 3-11, were prepared by following thesynthetic procedures of Scheme 2 below.

Example 3 Preparation ofN,N-diethyl-4-{-4(3-hydroxyphenyl)[1-(2-thienylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 10)

[0056] To a room temperature solution of secondary amine (600mg; 1.65mmol) in methanol (15 ml) was added thiophene-2-carboxaldehyde (153.8ul; 1.65 mmol), followed by acetic acid (1 ml). The mixture was stirredfor two hours then sodium cyanoborohydride (311 mg; 4.95 mmol) wasadded. The reaction mixture was stirred overnight, then water was addedand the mixture extracted with methylene chloride. Combined methylenechloride extracts were dried over anhydrous sodium sulphate, filteredand concentrated under reduced pressure. Reverse phase purification.

[0057] (M+1) calculated: 461.64, (M+1) observed: 461.06

[0058] Anal.: calculated for (C₂₈H₃₂N₂O₂S X 1.60 C₂HO₂F₃ X 0.20 H₂O):C:57.95%; H:5.30%; N:4.33%; found: C:57.90%; H:5.34%; N:4.36%

[0059]¹HNMR (CD₃OD): 7.54 (dd, 1H, J=5.2, 1.6 Hz), 7.25 (d, 2H, J=8Hz),7.23-7.24 (m, 1H), 7.15 (d, 2H, J=8 Hz), 7.03-7.08 (m, 2H), 6.58-6.62(dd, 1H, J=8.0, 2.8 Hz), 6.52-6.55 (dd, 1H, J=7.6, 1.6 Hz)), 6.44-6.46(dd, 1H, J=2.8, 1.6 Hz), 4.50 (s, 2H), 3.40-3.50 (m, 4H), 3.15-3.25 (m,2H), 2.95-3.05 (m, 2H), 2.60-2.80 (m, 2H), 2.35-2.45 (m, 2H), 1.10-1.15(m, 3H), 1.00-1.05 (m, 3H)

Example 4 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(3-thienylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 11)

[0060] To a room temperature solution of secondary amine (500 mg; 1.37mmol) in methanol (13 ml) was added thiophene-3-carboxaldehyde (144.0ul; 1.65 mmol), followed by acetic acid (1 ml). The mixture was stirredfor three hours then sodium cyanoborohydride (258 mg; 4.11 mmol) wasadded. The reaction mixture was stirred overnight, then water was addedand the mixture extracted with methylene chloride. The aqueous phase wasneutralized with potassium bicarbonate and was extracted again withmethylene chloride. Combined methylene chloride extracts were dried overanhydrous sodium sulphate, filtered and concentrated under reducedpressure. Reverse phase purification.

[0061] (M+1) calculated: 461.64, (M+1) observed: 461.07

[0062] Anal.: calculated for (C₂₈H₃₂N₂O₂S X 1.10 C₂HO₂F₃ X 0.50 H₂O):C:60.96%; H:5.78%; N:4.71%; found: C:60.97%; H:5.78%; N:4.65%

[0063]¹HNMR (CD₃OD): 7.59 (dd, 1H, J=3.2, 1.6Hz), 7.49 (dd, 1H, J=5.2,3.2Hz), 7.26(d, 2H, J=8.0 Hz), 7.16 (d, 2H, J=8.0 Hz), 7.15 (m, 1H),7.07 (dd, 1H, J=8.0, 7.2 Hz), 6.61 (dd, 1H, J=8.0, 2.0 Hz), 6.55 (d, 1H,J=7.2 Hz), 6.47 (dd, 1H, J=2.0, 1.6 Hz), 4.29 (s, 2H), 3.40-3.50 (m,4H), 3.15-3.25 (m, 2H), 2.95-3.05 (m, 2H), 2.60-2.80 (m, 2H), 2.35-2.45(m, 2H), 1.15-1.20 (t, 3H, J=6.4 Hz), 1.00-1.05 (t, 3H, J=6.4 Hz)

Example 5 Preparation ofN,N-diethyl-4-[[1-(2-furylmethyl)-4-piperidinylidene](3-hydroxyphenyl)Methyl]Benzamide(Compound 12)

[0064] To a room temperature solution of secondary amine (500 mg; 1.37mmol) in methanol (13 ml) was added 2-furaldehyde (136.0 μl; 1.65 mmol),followed by acetic acid (1 ml). The mixture was stirred for three hoursthen sodium cyanoborohydride (258 mg; 4.11 mmol) was added. The reactionmixture was stirred overnight, then water was added and the mixtureextracted with methylene chloride. The aqueous phase was neutralizedwith potassium bicarbonate and was extracted again with methylenechloride. Combined methylene chloride extracts were dried over anhydroussodium sulphate, filtered and concentrated under reduced pressure.Reverse phase purification.

[0065] (M+1) calculated: 445.57, (M+1) observed: 445.13

[0066] Anal.: calculated for (C₂₈H₃₂N₂O₃ X 1.30 C₂HO₂F₃ X 0.10 H₂O):C:61.81%; H:5.68%; N:4.71%; found: C:61.88%; H:5.74%; N:4.73%

[0067]¹HNMR (CD₃OD): 7.58 (d, 1H, J=1.6 Hz), 7.26 (d, 2H, J=8.0 Hz),7.16 (d, 2H, J=8.0 Hz), 7.07 (t, 1H, J=8.0 Hz), 6.62-6.64 (m, 1H),6.60-6.61 (m, 1H), 6.53-6.55 (m, 1H), 6.46-6.47 (m, 1H), 6.43-6.45 (m,1H), 4.34 (s, 2H), 3.40-3.50 (m, 4H), 3.15-3.25 (m, 2H), 2.95-3.05 (m,2H), 2.55-2.80 (m, 2H), 2.35-2.50 (m, 2H), 1.15-1.20 (t, 3H, J=6.4 Hz),1.00-1.05 (t, 3H, J=6.4 Hz)

Example 6 Preparation ofN,N-diethyl-4-[[1-(3-furylmethyl)-4-piperidinylidene](3-hydroxyphenyl)Methyl]benzamide(Compound 13)

[0068] To a room temperature solution of secondary amine (300 mg; 0.82mmol) in methanol (8 ml) was added 3-furaldehyde (214.0 μl; 2.47 mmol),followed by acetic acid (0.5 ml) and sodium cyanoborohydride (1 55 mg;2.47 mmol). The reaction mixture was stirred overnight, quenched withsodium bicarbonate and extracted with methylene chloride. Combinedmethylene chloride extracts were dried over anhydrous sodium sulphate,filtered and concentrated under reduced pressure. Reverse phasepurification.

[0069] (M+1) calculated: 445.57, (M+1) observed: 445.15

[0070] Anal.: calculated for (C₂₈H₃₂N₂O₃ X 0.50 C₂HO₂F₃ X 0.10 H₂O):C:69.20%; H:6.55%; N:5.56%; found: C:69.14%; H:6.57%; N:5.28%

[0071]¹HNMR (CD₃OD): 7.75 (s, 1H), 7.61-7.62 (m, 1H), 7.33 (d, 2H, J=8.0Hz), 7.23 (d, 2H, J=8.0 Hz), 7.13 (dd, 1H, J=8.4, 8.0 Hz), 6.66-6.69 (m,1H), 6.57-6.63 (m, 2H), 6.51-6.53 (m, 1H), 4.22 (s, 2H), 3.45-3.55 (m,4H), 3.25-3.30 (m, 2H), 2.95-3.10 (m, 2H), 2.65-2.85 (m, 2H), 2.40-2.55(m, 2H), 1.15-1.25 (m, 3H), 1.05-1.15 (m, 3H)

Example 7 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(2-pyridinylmethyl)-4-piperidinylidene]methyl}benzamide(Compound 14)

[0072] To a room temperature solution of secondary amine (384.3 mg; 1.05mmol) in methanol (10 ml) was added 2-pyridinecarboxaldehyde (201.0 μl;2.11 mmol), followed by acetic acid (1 ml). The mixture was stirred for30 minutes then sodium cyanoborohydride (199 mg; 3.16 mmol) was added.The reaction mixture was stirred overnight, then water was added and themixture extracted with methylene chloride. The aqueous phase wasneutralized with sodium bicarbonate and was extracted again withmethylene chloride. Combined methylene chloride extracts were dried overanhydrous sodium sulphate, filtered and concentrated under reducedpressure. Reverse phase purification.

[0073] (M+1) calculated: 456.60, (M+1) observed: 456.12

[0074] Anal.: calculated for (C₂₉H₃₃N₃O₂ X 1.70 C₂HO₂F₃ X 0.40 H₂O):C:59.26%; H:5.45%; N:6.40%; found: C:59.21%; H:5.46%; N:6.35%

[0075]¹HNMR (CD₃OD): 8.57 (d, 1H, J=5.2Hz), 7.78 (dt, 1H, J=8.0, 1.2Hz), 7.38 (d, 1H, J=8.0 Hz), 7.34 (dd, 1H, J=8.0, 5.2 Hz), 7.24 (d, 2H,J=8.0 Hz), 7.15 (d, 2H, J=8.0 Hz), 7.05 (t, 1H, J=8.0 Hz), 6.59 (dd, 1H,J=8.0, 2.4 Hz), 6.54 (d, 1H, J=8.0 Hz), 6.45 (dd, 1H, J=2.4, 1.2 Hz),4.39 (s, 2H), 3.40-3.46 (m, 2H), 3.26-3.34 (m, 4H), 3.16-3.22 (m, 2H),2.54-2.64 (m, 4H), 1.13 (t, 3H, J=6.4 Hz), 1.01 (t, 3H, J=6.4 Hz)

Example 8 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(4-pyridinylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 15)

[0076] To a room temperature solution of secondary amine (300 mg; 0.82mmol) in methanol (8 ml) was added 4-pyridinecarboxaldehyde (236 μl;2.47 mmol), followed by acetic acid (0.5 ml). The mixture was stirredfor 30 minutes then sodium cyanoborohydride (155 mg; 2.47 mmol) wasadded. The reaction mixture was stirred overnight, quenched with sodiumbicarbonate and extracted with methylene chloride. Combined methylenechloride extracts were dried over anhydrous sodium sulphate, filteredand concentrated under reduced pressure. Reverse phase purification.

[0077] (M+1) calculated: 456.60, (M+1) observed: 456.10

[0078] Anal.: calculated for (C₂₉H₃₃N₃O₂ X 1.80 C₂HO₂F₃ X 0.40 H₂O):C:58.61%; H:5.37%; N:6.29%; found: C:58.64%; H:5.32%; N:6.46%

[0079]¹HNMR (CD₃OD): 8.64 (s, 2H), 7.61 (d, 2H, J=5.2Hz), 7.25 (2H,J=8.0 Hz), 7.14 (d, 2H, J=8.0 Hz), 7.05 (t, 1H, J=8.0 Hz), 6.59 (dd, 1H,J=8.0, 1.6 Hz), 6.53 (d, 1H, J=8.0 Hz), 6.43-6.46 (m, 1H), 4.34 (s, 2H),3.42-3.44 (m, 2H), 3.18-3.24 (m, 6H), 2.54-2.57 (m, 4H), 1.13 (t, 3H,J=6.4 Hz), 1.02 (t, 3H, J=6.4 Hz)

Example 9 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(1H-imidazol-2-ylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 16)

[0080] To a room temperature solution of secondary amine (300 mg; 0.82mmol) in methanol (8 ml) was added 2-imidazolecarboxaldehyde (237.3 mg;2.47 mmol), followed by acetic acid (0.5 ml) and sodium cyanoborohydride(155 mg; 2.47 mmol). The reaction mixture was stirred overnight,quenched with sodium bicarbonate and extracted with methylene chloride.Combined methylene chloride extracts were dried over anhydrous sodiumsulphate, filtered and concentrated under reduced pressure. Reversephase purification.

[0081] (M+1) calculated: 445.58, (M+1) observed: 445.16

[0082] Anal.: calculated for (C₂₇H₃₂N₄O₂ X 2.10 C₂HO₂F₃ X 0.50 H₂O):C:54.07%; H:5.11%; N:8.08%; found: C:54.04%; H:5.05%; N:8.09%

[0083]¹HNMR (CD₃OD): 7.38 (s, 2H), 7.20-7.22 (m, 2H), 7.11 (d, 2H, J=8.0Hz), 7.0 (t, 1H, J=8.0 Hz), 6.55 (dd, 1H, J=8.0, 3.6 Hz), 6.49-6.50 (m,1H), 6.42-6.43 (m, 1H), 4.08 (s, 2H), 3.41-3.43 (m, 2H), 3.18-3.20 (m,3H), 2.79-2.82 (m, 4H), 2.39-2.45 (m, 4H). 1.08-1.16 (m, 3H), 0.96-1.16(m, 3H)

Example 10 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(1H-imidazol-4-ylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 17)

[0084] To a room temperature solution of secondary amine (300 mg; 0.82mmol) in methanol (10 ml) was added 4(5)-imidazolecarboxaldehyde (94.9mg; 0.99 mmol), followed by acetic acid (0.5 ml). The mixture wasstirred 1 hour then sodium cyanoborohydride (62.1 mg; 0.99 mmol). Thereaction mixture was stirred overnight, quenched with sodium bicarbonateand extracted with methylene chloride. Combined methylene chlorideextracts were dried over anhydrous sodium sulphate, filtered andconcentrated under reduced pressure. Reverse phase purification.

[0085] (M+1) calculated: 445.58, (M+1) observed: 445.16

[0086] Anal.: calculated for (C₂₇H₃₂N₄O₂ X 2.20 C₂HO₂F₃): C:54.23%;H:4.96%; N:8.06%; found: C:54.43%; H:4.99%; N:7.73%

[0087]¹HNMR (CD₃OD): 8.54 (s, 1H), 7.57 (s, 1H), 7.23 (d, 2H, J=8.4 Hz),7.13 (d, 2H, J=8.0 Hz), 7.03 (dd, 1H, J=8.0, 7.6 Hz), 6.57-6.59 (m, 1H),6.51-6.53 (m, 1H), 6.43-6.44 (m, 1H), 4.35 (s, 2H), 3.41-3.43 (m, 2H),3.18-3.23 (m, 8H), 2.53-2.56 (m, 4H), 1.08-1.16 (m, 3H), 0.96-1.04 (m,3H)

Example 11 Preparation ofN,N-diethyl-4-{(3-hydroxyphenyl)[1-(1,3-thiazol-2-ylmethyl)-4-piperidinylidene]Methyl}Benzamide(Compound 18)

[0088] To a room temperature solution of secondary amine (143.2 mg; 0.39mmol) in methanol (4 ml) was added 2-thiazolecarboxaldehyde (41.4 ul;0.47 mmol), followed by acetic acid (0.2 ml). The mixture was stirred 1hour then sodium cyanoborohydride (129.6 mg; 1.48 mmol). The reactionmixture was stirred overnight, quenched with sodium bicarbonate andextracted with methylene chloride. Combined methylene chloride extractswere dried over anhydrous sodium sulphate, filtered and concentratedunder reduced pressure. Reverse phase purification.

[0089] (M+1) calculated: 462.63, (M+1) observed: 462.10

[0090] Anal.: calculated for (C₂₇H₃₁N₃O₂S X 1.10 C₂HO₂F₃ X 1.10 H₂O):C:57.79%; H:5.70%; N:6.92%; found: C:57.75%; H:5.60%; N:7.13%

[0091]¹HNMR (CD₃OD): 7.86 (d, 1H, J=4.0 Hz), 7.68 (d, 1H, J=4.0 Hz),7.26 (d, 2H, J=8.0 Hz), 7.16 (d, 2H, J=8.0 Hz), 7.07 (dd, 1H, J=8.4, 8.0Hz), 6.60-6.62 (m, 1H), 6.54-6.56 (m, 1H), 6.46-6.47 (m, 1H), 4.65 (s,2H), 3.21-3.45 (m, 8H), 2.56-2.58 (m, 4H), 1.12-1.20 (m, 3H), 1.00-1.08(m, 3H)

Pharmaceutical compositions

[0092] The novel compounds according to the present invention may beadministered orally, intramuscularly, subcutaneously, topically,intranasally, intraperitoneally, intrathoracially, intravenously,epidurally, intrathecally, intracerebroventricularly and by injectioninto the joints.

[0093] A preferred route of administration is orally, intravenously orintramuscularly.

[0094] The dosage will depend on the route of administration, theseverity of the disease, age and weight of the patient and other factorsnormally considered by the attending physician, when determining theindividual regimen and dosage level as the most appropriate for aparticular patient.

[0095] For preparing pharmaceutical compositions from the compounds ofthis invention, inert, pharmaceutically acceptable carriers can beeither solid or liquid. Solid form preparations include powders,tablets, dispersible granules, capsules, cachets, and suppositories.

[0096] A solid carrier can be one or more substances which may also actas diluents, flavoring agents, solubilizers, lubricants, suspendingagents, binders, or tablet disintegrating agents; it can also be anencapsulating material.

[0097] In powders, the carrier is a finely divided solid which is in amixture with the finely divided active component. In tablets, the activecomponent is mixed with the carrier having the necessary bindingproperties in suitable proportions and compacted in the shape and sizedesired.

[0098] For preparing suppository compositions, a low-melting wax such asa mixture of fatty acid glycerides and cocoa butter is first melted andthe active ingredient is dispersed therein by, for example, stirring.The molten homogeneous mixture is then poured into convenient sizedmolds and allowed to cool and solidify.

[0099] Suitable carriers are magnesium carbonate, magnesium stearate,talc, lactose, sugar, pectin, dextrin, starch, tragacanth, methylcellulose, sodium carboxymethyl cellulose, a low-melting wax, cocoabutter, and the like.

[0100] Salts include, but are not limited to, pharmaceuticallyacceptable salts. Examples of pharmaceutically acceptable salts withinthe scope of the present invention include: acetate, benzenesulfonate,benzoate, bicarbonate, bitartrate, bromide, calcium acetate, camsylate,carbonate, chloride, citrate, dihydrochloride, edetate, edisylate,estolate, esylate, fumarate, glucaptate, gluconate, glutamate,glycollylarsanilate, hexylresorcinate, hydrabamine, hydrobromide,hydrochloride, hydroxynaphthoatc, isethionate, lactate, lactobionate,malate, maleate, mandelate, mesylate, methylbromide, methylnitrate,methylsulfate, mucate, napsylate, nitrate, pamoate (embonate),pantothenate, phosphate/diphosphate, polygalacturonate, salicylate,stearate, subacetate, succinate, sulfate, tannate, tartrate, teoclate,triethiodide, benzathine, chloroprocaine, choline, diethanolamine,ethylenediamine, meglumine, procaine, aluminium, calcium, lithium,magnesium, potassium, sodium, and zinc.

[0101] Examples of phannaceutically unacceptable salts within the scopeof the present invention include: hydroiodide, perchlorate,tetrafluoroborate.

[0102] Preferred pharmaceutically acceptable salts are hydrochlorides,sulfates and bitartrates. The hydrochloride and sulfate salts areparticularly preferred.

[0103] The term composition is intended to include the formulation ofthe active component with encapsulating material as a carrier providinga capsule in which the active component (with or without other carriers)is surrounded by a carrier which is thus in association with it.Similarly, cachets are included.

[0104] Tablets, powders, cachets, and capsules can be used as soliddosage forms suitable for oral administration.

[0105] Liquid from compositions include solutions, suspensions, andemulsions. Sterile water or water-propylene glycol solutions of theactive compounds may be mentioned as an example of liquid preparationssuitable for parenteral administration. Liquid compositions can also beformulated in solution in aqueous polyethylene glycol solution.

[0106] Aqueous solutions for oral administration can be prepared bydissolving the active component in water and adding suitable colorants,flavoring agents, stabilizers, and thickening agents as desired. Aqueoussuspensions for oral use can be made by dispersing the finely dividedactive component in water together with a viscous material such asnatural synthetic gums, resins, methyl cellulose, sodium carboxymethylcellulose, and other suspending agents known to the pharmaceuticalformulation art.

[0107] Preferably the pharmaceutical compositions is in unit dosageform. In such form, the composition is divided into unit dosescontaining appropriate quantities of the active component. The unitdosage form can be a packaged preparation, the package containingdiscrete quantities of the preparations, for example, packeted tablets,capsules, and powders in vials or ampoules. The unit dosage form canalso be a capsule, cachet, or tablet itself, or it can be theappropriate number of any of these packaged forms.

BIOLOGICAL EVALUATION In Vitro Model Cell Culture

[0108] A. Human 293S cells expressing cloned human μ, δ, and κ receptorsand neomycin resistance were grown in suspension at 37° C. and 5% CO₂ inshaker flasks containing calcium-free DMEM10% FBS, 5% BCS, 0.1% PluronicF-68, and 600 μg/ml geneticin.

[0109] B. Mouse and rat brains were weighed and rinsed in ice-cold PBS(containing 2.5 mM EDTA, pH 7.4). The brains were homogenized with apolytron for 15 sec (mouse) or 30 sec (rat) in ice-cold lysis buffer (50mM Tris, pH 7.0, 2.5 mM EDTA, with phenylmethylsulfonyl fluoride addedjust prior use to 0.5 MmM from a 0.5M stock in DMSO:ethanol).

Membrane preparation

[0110] Cells were pelleted and resuspended in lysis buffer (50 mM Tris,pH 7.0, 2.5 mM EDTA, with PMSF added just prior to use to 0.1 mM from a0.1 M stock in ethanol), incubated on ice for 15 min, then homogenizedwith a polytron for 30 sec. The suspension was spun at 1,000g (max) for10 min at 4° C. The supernatant was saved on ice and the pelletsresuspended and spun as before. The supernatants from both spins werecombined and spun at 46,000 g(max) for 30 min. The pellets wereresuspended in cold Tris buffer (50 mM Tris/Cl, pH 7.0) and spun again.The final pellets were resuspended in membrane buffer (50 mM Tris, 0.32M sucrose, pH 7.0). Aliquots (1 ml) in polypropylene tubes were frozenin dry ice/ethanol and stored at −70° C. until use. The proteinconcentrations were determined by a modified Lowry assay with SDS.

Binding assays

[0111] Membranes were thawed at 37° C., cooled on ice, passed 3 timesthrough a 25-gauge needle, and diluted into binding buffer (50 mM Tris,3 mM MgCl₂, 1 mg/ml BSA (Sigma A-7888), pH 7.4, which was stored at 4°C. after filtration through a 0.22 m filter, and to which had beenfreshly added 5 μg/ml aprotinin, 10 μM bestatin, 10 μM diprotin A, noDTT). Aliquots of 100 μl were added to iced 12×75 mm polypropylene tubescontaining 100 μl of the appropriate radioligand and 100 μl of testcompound at various concentrations. Total (TB) and nonspecific (NS)binding were determined in the absence and presence of 10 μM naloxonerespectively. The tubes were vortexed and incubated at 25° C. for 60-75min, after which time the contents are rapidly vacuum-filtered andwashed with about 12 ml/tube iced wash buffer (50 mM Tris, pH 7.0, 3 mMMgCl₂) through GF/B filters (Whatman) presoaked for at least 2h in 0.1%polyethyleneimine. The radioactivity (dpm) retained on the filters wasmeasured with a beta counter after soaking the filters for at least 12hin minivials containing 6-7 ml scintillation fluid. If the assay is setup in 96-place deep well plates, the filtration is over 96-placePEI-soaked unifilters, which were washed with 3×1 ml wash buffer, anddried in an oven at 55° C. for 2h. The filter plates were counted in aTopCount (Packard) after adding 50 μl MS-20 scintillation fluid/well.

Functional Assays

[0112] The agonist activity of the compounds is measured by determiningthe degree to which the compounds receptor complex activates the bindingof GTP to G-proteins to which the receptors are coupled. In the GTPbinding assay, GTP[Δ]³⁵S is combined with test compounds and membranesfrom HEK-293S cells expressing the cloned human opioid receptors or fromhomogenised rat and mouse brain. Agonists stimulate GTP[Δ]³⁵S binding inthese membranes. The EC₅₀ and E_(max) values of compounds are determinedfrom dose-response curves. Right shifts of the dose response curve bythe delta antagonist naltrindole are performed to verify that agonistactivity is mediated through delta receptors.

Data analysis

[0113] The specific binding (SB) was calculated as TB-NS, and the SB inthe presence of various test compounds was expressed as percentage ofcontrol SB. Values of IC₅₀ and Hill coefficient (n_(H)) for ligands indisplacing specifically bound radioligand were calculated from logitplots or curve fitting programs such as Ligand, GraphPad Prism,SigmaPlot, or ReceptorFit. Values of K_(i) were calculated from theCheng-Prussoff equation. Mean±S.E.M. values of IC₅₀, K_(i) and n_(H)were reported for ligands tested in at least three displacement curves.Biological data are tabulated in Table 1 on the following pages. TABLE 1Biological data HDELTA RAT BRAIN MOUSE BRAIN EX. MOLECULAR STRUCTUREHDELTA EC50 % E Max EC50 % E Max EC50 % E Max 2

0.408 0.1 104.09 0.6 112.2 0.79 103.77 3

0.521 0.15 98.18 0.93 167.51 1.52 186.36 4

0.366 5

0.266 0.09 94.78 0.81 132.09 1.07 134.16 6

0.196 7

0.209 0.07 103.29 0.33 134.88 0.55 137.63 8

0.346 0.3 112.34 3.3 81.44 4.65 78.19 9

0.117 0.27 106.1 0.68 151.01 0.81 135.96 10

0.172 0.48 107.23 4.64 101.93 5.06 103.53 11

0.282 0.34 115.37 2.99 119.82 2.19 117.99

Receptor saturation experiments

[0114] Radioligand K_(δ) values were determined by performing thebinding assays on cell membranes with the appropriate radioligands atconcentrations ranging from 0.2 to 5 times the estimated K_(δ) (up to 10times if amounts of radioligand required are feasible). The specificradioligand binding was expressed as pmole/mg membrane protein. Valuesof Kδ and B_(max) from individual experiments were obtained fromnonlinear fits of specifically bound (B) vs. nM free (F) radioligandfrom individual according to a one-site model.

Determination of Mechano-allodynia using Von Frey Testing

[0115] Testing was performed between 08:00 and 16:00h using the methoddescribed by Chaplan et al. (1994). Rats were placed in Plexiglas cageson top of a wire mesh bottom which allowed access to the paw, and wereleft to habituate for 10-15 min. The area tested was the mid-plantarleft hind paw, avoiding the less sensitive foot pads. The paw wastouched with a series of 8 Von Frey hairs with logarithmicallyincremental stiffness (0.41, 0.69, 1.20, 2.04, 3.63, 5.50, 8.51, and15.14 grams; Stoelting, Ill., USA). The von Frey hair was applied fromunderneath the mesh floor perpendicular to the plantar surface withsufficient force to cause a slight buckling against the paw, and heldfor approximately 6-8 seconds. A positive response was noted if the pawwas sharply withdrawn. Flinching immediately upon removal of the hairwas also considered a positive response. Ambulation was considered anambiguous response, and in such cases the stimulus was repeated.

Testing Protocol

[0116] The animals were tested on postoperative day 1 for theFCA-treated group. The 50% withdrawal threshold was determined using theup-down method of Dixon (1980). Testing was started with the 2.04 ghair, in the middle of the series. Stimuli were always presented in aconsecutive way, whether ascending or descending. In the absence of apaw withdrawal response to the initially selected hair, a strongerstimulus was presented; in the event of paw withdrawal, the next weakerstimulus was chosen. Optimal threshold calculation by this methodrequires 6 responses in the immediate vicinity of the 50% threshold, andcounting of these 6 responses began when the first change in responseoccurred, e.g. the threshold was first crossed. In cases wherethresholds fell outside the range of stimuli, values of 15.14 (normalsensitivity) or 0.41 (maximally allodynic) were respectively assigned.The resulting pattern of positive and negative responses was tabulatedusing the convention, X=no withdrawal; O=withdrawal, and the 50%withdrawal threshold was interpolated using the formula:

50% g threshold=10^((Xf+kδ))/10,000

[0117] where Xf=value of the last von Frey hair used (log units);k=tabular value (from Chaplan et al. (1994)) for the pattern ofpositive/negative responses; and δ=mean difference between stimuli (logunits). Here δ=0.224.

[0118] Von Frey thresholds were converted to percent of maximum possibleeffect (% MPE), according to Chaplan et al. 1994. The following equationwas used to compute % MPE:${\% \quad {MPE}} = {\frac{{{Drug}\quad {treated}\quad {{threshold}(g)}} - {{allodynia}\quad {{threshold}(g)}}}{{{Control}\quad {{threshold}(g)}} - {{allodynia}\quad {{threshold}(g)}}} \times 100}$

Administration of Test Substance

[0119] Rats were injected (subcutaneously, intraperitoneally,intravenously or orally) with a test substance prior to von Freytesting, the time between administration of test compound and the vonFrey test varied depending upon the nature of the test compound.

Writhing Test

[0120] Acetic acid will bring abdominal contractions when administeredintraperitoneally in mice. These will then extend their body in atypical pattern. When analgesic drugs are administered, this describedmovement is less frequently observed and the drug selected as apotential good candidate.

[0121] A complete and typical Writhing reflex is considered only whenthe following elements are present: the animal is not in movement; thelower back is slightly depressed; the plantar aspect of both paws isobservable. In this assay, compounds of the present inventiondemonstrate significant inhibition of writhing responses after oraldosing of 1 -100 μmol/kg.

[0122] (i) Solutions preparation

[0123] Acetic acid (AcOH): 120 μL of Acetic Acid is added to 19.88 ml ofdistilled water in order to obtain a final volume of 20 ml with a finalconcentration of 0.6% AcOH. The solution is then mixed (vortex) andready for injection.

[0124] Compound (drug): Each compound is prepared and dissolved in themost suitable vehicle according to standard procedures.

[0125] (ii) Solutions administration

[0126] The compound (drug) is administered orally, intraperitoneally(i.p.) , subcutaneously (s.c.) or intravenously (i.v.)) at 10 ml/kg(considering the average mice body weight) 20, 30 or 40 minutes(according to the class of compound and its characteristics) prior totesting. When the compound is delivered centrally: Intraventricularly(i.c.v.) or intrathecally (i.t.) a volume of 5 μL is administered.

[0127] The AcOH is administered intraperitoneally (i.p.) in two sites at10 ml/kg (considering the average mice body weight) immediately prior totesting.

(iii) Testing

[0128] The animal (mouse) is observed for a period of 20 minutes and thenumber of occasions (Writhing reflex) noted and compiled at the end ofthe experiment. Mice are kept in individual “shoe box” cages withcontact bedding. A total of 4 mice are usually observed at the sametime: one control and three doses of drug.

1. A compound of the formula I

wherein R¹ is selected from any one of

where each R¹ phenyl ring and R¹ heteroaromatic ring may independentlybe further substituted by 1, 2 or 3 substituents selected from straightand branched C₁-C₆ alkyl, NO₂, CF₃, C₁-C₆ alkoxy, chloro, fluoro, bromo,and iodo, as well as salts is thereof.
 2. A compound according to claim1, wherein each R¹ phenyl ring and R¹ heteroaromatic ring mayindependently be further substituted by 1, 2 or 3 substituents selectedfrom methyl, CF₃, chloro, fluoro, bromo, and iodo.
 3. A compoundaccording to claim 1, wherein each R¹ phenyl ring and R¹ heteroaromaticring may independently be further substituted by a methyl group.
 4. Acompound according to claim 1, wherein R¹ is pyridinyl, thienyl orfuranyl.
 5. A compound according to claim 1, selected from any one ofN,N-Diethyl-4-(3-hydroxylphenyl-N-benzyl-piperidin-4-ylidene-methyl)-benzamide;N,N-diethyl-4-{(3-hydroxyphenyl)[1-(2-thienylmethyl)-4-piperidinylidene]methyl}benzamide;N,N-diethyl-4-{(3-hydroxyphenyl)[1-(3-thienylmethyl)-4-piperidinylidene]methyl}benzamide;N,N-diethyl-4-[[1-(2-furylmethyl)-4-piperidinylidene](3-hydroxyphenyl)methyl]benzamide;N,N-diethyl-4-[[1-(3-furylmethyl)-4-piperidinylidene](3-hydroxyphenyl)methyl]benzamide;N,N-diethyl-4-{(3-hydroxyphenyl)[1-(2-pyridinylmethyl)-4-piperidinylidene]methyl }benzamide;N,N-diethyl-4-{(3-hydroxyphenyl)[1-(4-pyridinylmethyl)-4-piperidinylidene]methyl }benzamide;N,N-diethyl-4-{(3-hydroxyphenyl)[1 -(1H-imidazol-2-ylmethyl)-4-piperidinylidene]methyl}benzamide;N,N-diethyl-4-{(3 -hydroxyphenyl)[1 -(1H-imidazol-4-ylmethyl)-4-piperidinylidene]methyl}benzamide; andN,N-diethyl-4-{(3-hydroxyphenyl)[1-(1,3-thiazol-2-ylmethyl)-4-piperidinylidene]methyl}benzamide.
 6. A compound according to any of the preceding claims, inform of its hydrochloride, dihydrochloride, sulfate, tartrate,ditrifluoroacetate or citrate salts.
 7. A process for preparing acompound of formula I, comprising the reaction of, reacting a compoundof the general formula II

wherein PG is a urethane or benzyl-like protecting group, such as Boc,with 3-hydroxyphenyl boronic acid, using a palladium catalyst in thepresence of a base to give the compounds of general formula III,

which is thereafter deprotected, under standard conditions and alkylatedunder reductive conditions with a compound of the general formula R¹-CHOto give compounds of the general formula I.
 8. A compound according toclaim 1 for use in therapy.
 9. A compound according to claim 8, whereinthe therapy is pain management.
 10. A compound according to claim 8,wherein the therapy is directed towards gastrointestinal disorders. 11.A compound according to claim 8, wherein the therapy is directed towardsspinal injuries.
 12. A compound according to claim 8, wherein thetherapy is directed to disorders of the sympathetic nervous system. 13.Use of a compound according to formula I of claim 1 for the manufactureof a medicament for use in the treatment of pain, gastrointestinaldisorders or spinal injuries.
 14. A pharmaceutical compositioncomprising a compound of the formula I according to claim 1 as an activeingredient, together with a pharmaceutically acceptable carrier.
 15. Amethod for the treatment of pain, whereby an effective amount of acompound of the formula I according to claim 1 is administered to asubject in need of pain management.
 16. A method for the treatment ofgastrointestinal disorders, whereby an effective amount of a compound ofthe formula I according to claim 1, is administered to a subjectsuffering from said gastrointestinal disorder.
 17. A method for thetreatment of spinal injuries, whereby an effective amount of a compoundof the formula I according to claim 1, is administered to a subjectsuffering from said spinal injury.
 18. A compound of the general formulaII

wherein PG is a urethane or benzyl-like protecting group.